1. Field of the Invention
The present invention relates generally to systems and apparatus for leveling a motor vehicle or trailer on sloping terrain, and more specifically to a system and apparatus for automatically laterally leveling the bed of a semi dump trailer when dumping operations are underway. The apparatus automatically compensates for the lateral tilt of the trailer frame when dumping is taking place on sloping terrain, and automatically discontinues dumping operations if a predetermined lateral slope is exceeded. Warning means may be included if a predetermined lateral slope is exceeded.
2. Description of the Related Art
Trucks having rearwardly tilting boxes or beds have been in use for some time, for use in carrying and dumping large quantities of materials (gravel, sand, dirt, etc.) in construction work and the like, hauling agricultural material, trash and refuse, scrap metal, etc. Most such trucks comprise an integrated vehicle having a single, unitary frame for the cab and dump body, with no separate trailer. Such vehicles generally have a relatively short dump box, with the box not extending to any great height when raised for dumping.
However, the development of larger dump vehicles comprising a relatively long semi trailer towed behind a semi truck, has permitted dump body trailers to be developed which have considerably more capacity and which are considerably longer than the more common unitary dump truck. When the forward end of the dump box of such a trailer is raised in order to tilt the box rearwardly for dumping the contents thereof, the forward end of the elongate dump box is raised to a considerable height, perhaps thirty feet or more above the surrounding terrain. While the dump box would not normally be raised to its maximum slope immediately with a full load therein, the dump box will still have a fair quantity of material therein when it is raised to its maximum extent, and in any event, the structure of the dump box itself is relatively heavy in order to provide the required structural strength for the vehicle.
It will be seen that the center of gravity of the partially laden dump box is elevated considerably above the underlying surface of the vehicle, and that any lateral slope upon which the semi truck is parked during dumping, will cause the center of gravity of the dump box (and thus of the entire vehicle of which the dump box is a part) to be laterally shifted toward the downhill side of the slope. If the dump box is raised sufficiently high and has a sufficiently heavy load therein, and the slope is sufficiently steep, this can easily lead to the entire semi truck and trailer tipping over, even though the slope may have been easily negotiable with the trailer in its lowered position.
It should be noted that the types of operations and materials for which such semi truck dump trailers are frequently used, often result in the dumping of materials in relatively unstable areas (soft farm fields, road and building construction sites, and particularly, sanitary landfills). Even when the slope initially appears sufficiently shallow to allow the dump box to be raised to its maximum extent, the rearward shift of the center of gravity of the trailer as the dump box is tilted upwardly and rearwardly, will place additional weight on the rear wheels of the vehicle. This can often result in further settling of the ground beneath the rear wheels of the trailer, particularly on the low side of the trailer as the center of gravity shifts laterally when the box is raised.
Accordingly, various mechanisms have been developed in the past for leveling at least the dump box of such a semi trailer dump vehicle, and/or for warning the operator of the vehicle if the slope is hazardous. The present inventor is aware of many such mechanisms providing for such leveling or warning, but in each case, the related art device fails to provide for all of the features required of such a mechanism, such as a slight time delay to allow for settling of the vehicle wheels as the dump box is initially tilted, automatic stopping of the operation if a predetermined slope is reached or exceeded, and other features providing optimum operational efficiency of such a system. A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,044,832 issued on Jul. 17, 1962 to Frank C. McManus, titled "Fluid Stabilizing Means For Semi-Trailer Tilting Bodies," describes hydraulic and manual means for leveling a tilting semi trailer body by applying bracing against the outboard tires of the trailer. No automated means of determining a level position for the trailer, is disclosed. The use of bracing against the treads of pneumatic tires produces less than optimum stability for the assembly, as the tires themselves would distort as the load placed upon them varies according to shifting of the load as it dumps, wind loads, etc. The present invention provides a fully automated means of leveling a semi dump trailer by applying hydraulic force between the dump box and the underlying frame, or between the frame and the axle(s).
U.S. Pat. No. 3,203,735 issued on Aug. 31, 1965 to Petrus A. Vestin, titled "Fluid Operated Tilting Dump Truck Stabilizer," describes a system for locking the rear suspension of the truck in the loaded or compressed position during dumping operations. The rear suspension of the truck remains compressed during the time the dump box is raised and the load is emptied therefrom, with the spring compression being released when the empty box is lowered to its rest position. However, the Vestin system does not operate like the present system, in that it does not provide for any differential adjustment of the dump box tilt. The Vestin system operates on both sides of the suspension equally, with no lateral differential provided. Also, Vestin does not disclose any means for adjusting the suspension while the box is elevated.
U.S. Pat. No. 3,464,755 issued on Sep. 2, 1969 to Edward Brown, titled "Dump Trailer Safety Device," describes a system for automatically lowering the dump box of a semi trailer dump rig. If a predetermined tilt angle is reached, the Brown system overrides the manual dump box control and automatically lowers the trailer dump box. However, Brown does not provide any lateral adjustment means in his system, as provided by the present invention. A truck using the Brown system would have to be repositioned by the driver, which would take up additional time during the dumping operation, and likely delay other trucks waiting to dump in the same area. The present system includes means for automatically leveling the trailer dump box, or at least positioning the dump box within predetermined lateral angular limits, unlike the Brown system.
U.S. Pat. No. 3,921,128 issued on Nov. 18, 1975 to Edwin DeS. Snead, titled "Truck Roll Warning System," describes a system using a pair of mercury switches as leveling switches and mounted to the tilting dump box of the truck. The switches are connected to a warning means to warn the vehicle operator if the truck exceeds a predetermined lateral slope with the dump box lowered. As the dump box is raised, the angle of the mercury switch tubes is lowered relative to the horizontal, resulting in a smaller lateral tilt angle being required to set off the alarm. The system also automatically retracts the dump box when it is activated and the box is raised. No means for automatically leveling the truck trailer is provided by Snead.
U.S. Pat. No. 4,036,528 issued on Jul. 19, 1977 to Heinrich Langendorf, titled "Truck With Tiltable Body," describes a system wherein the dump box and frame are pivoted on a longitudinal axis. One or more hydraulic struts are used to level the dump box relative to the underlying axle and structure. Langendorf notes that some automatic means of leveling the dump box would be preferable (column 2, lines 21-24), but does not disclose any means of accomplishing such automated leveling. Moreover, no means of detecting when the dump box is not level (mercury level switches, etc.) is disclosed by Langendorf.
U.S. Pat. No. 4,705,295 issued on Nov. 10, 1987 to Gerald E. Fought, titled "Material Handling Vehicle Stabilizer," describes a system adapted for use with vehicles having remotely operated booms, cranes, buckets, and the like. Such devices can upset the vehicle upon which they are mounted when they are displaced laterally from the vehicle, and some stabilizing means is desirable for such vehicles, just as in the case of the dump trailers to which the present invention is applied. However, the Fought system serves to lock hydraulically the hydraulic suspension members of the vehicle when the remote control system is activated. Such a system is not desirable for a dump trailer vehicle operating on potentially unstable terrain, where it is desirable to provide a continuous, automatic means of adjusting for the tilt of the vehicle. The present invention provides such automatic lateral adjustment for the rear axle of the dump trailer, as well as other advantages not provided by the Fought system.
U.S. Pat. No. 4,145,682 issued on Mar. 20, 1979 to John Cook, titled "Semi-Dump Truck Level Indicator," describes a device containing a pair of mercury operated level switches for activating a warning in the vehicle cab. The Cook system does not involve any pneumatic or hydraulic systems for actually leveling the vehicle, as provided by the present invention. Rather, the Cook system only provides a warning to the vehicle operator if the dump body is tilted laterally either left or right to a predetermined point. The same problem results with the Cook system as with the system of the Brown '755 U.S. Patent discussed further above, in that the vehicle operator would have to reposition the vehicle when the warning was activated, thus taking further time for the dumping operation.
U.S. Pat. No. 4,261,616 issued on Apr. 14, 1981 to William I. Beegle, titled "Apparatus For Preventing The Tipping Of Dump Vehicles," describes a mechanical system for operating a relief valve in the hydraulic strut for raising the dump body of the truck. If an excessive weight differential occurs between the two sides of the dump body, indicating excessive lean or tilt toward the heavier side due to suspension compression, the linkage causes a valve to turn, thereby releasing the hydraulic pressure in the lift strut. The same problems result here as in the Brown '755 and Cook '682 U.S. Patents, in that no means is provided for leveling the dump box relative to the rest of the vehicle, as provided by the present invention. Thus, a vehicle equipped with the Beegle system would have to be moved before dumping could be continued.
U.S. Pat. No. 4,375,903 issued on Mar. 8, 1983 to Patrick A. Lovell, titled "Vehicle Suspension System Augmenter," describes a system of hydraulic jacks located at the rear axle(s) of the vehicle or vehicle trailer. The system includes means for retracting the jacks so they remain clear of all opposite frame or suspension members when not in use, thus reducing wear and tear on the system. The present invention also utilizes means for retracting the hydraulic struts to remain clear of other components when not in use. However, the present invention includes means for automatically leveling the dump trailer during dumping operations, and for warning the vehicle operator and/or discontinuing the dumping operation if a predetermined tilt angle is reached. Lovell does not disclose any system for automatically actuating his hydraulic jacks, as provided by the present invention.
U.S. Pat. No. 4,573,742 issued on Mar. 4, 1986 to Sheldon D. Tegtmeier, titled "Hydraulic Stabilizing Mechanism For Use With Hydraulic Elevating System," describes a hydraulic system in which a plurality of hydraulic struts are simultaneously extendible or retractable to bear against the bolster or axle of a wagon. No level sensing means is disclosed by Tegtmeier. Rather, the system merely extends all of the jacks simultaneously to lock the wagon body rigidly relative to the underlying axle(s). If lateral tilting of the wagon body produces a greater lateral differential force in the wagon, the Tegtmeier system cannot compensate for such. The present invention provides means for automatically adjusting the level of a trailer during the dumping operation.
U.S. Pat. No. 4,952,908 issued on Aug. 28, 1990 to John A. Sanner, titled "Trailer Stability Monitor," describes a system for alerting the operator of a tractor truck in motion, i.e., traveling along a roadway. The Sanner system is adapted for detecting an incipient rollover of the trailer portion of the rig, and sending a signal to the cab to alert the driver. The system depends upon the driver to reduce speed and/or increase the turning radius, and/or to take some corrective action to reduce the lateral centrifugal forces acting on the trailer. While the Sanner system would provide a warning of excessive trailer tilt for dumping operations, it does nothing to level the trailer or to stop the operation of the trailer, as does the present invention. A vehicle operator would likely not have sufficient time to lower the lift box in the event of a warning by the Sanner device.
Soviet Patent Publication No. 1,289,734 published on Feb. 15, 1987 illustrates a hydraulically actuated stabilizing system wherein a pair of laterally opposed hydraulic struts are extended to make ground contact, before dumping operations may occur. The lateral cylinders must contact the ground and build up a predetermined amount of pressure before the dump box lift strut may be activated. No automatic leveling of the dump trailer is indicated, as provided by the present invention. The present inventor is aware of vehicles using such lateral struts, but such assemblies are excessively complex and require excessive time for deployment and retraction for dumping operations, and are not in general use with tractor trailers with dump trailer bodies.
British Patent Publication No. 2,202,497 published on Sep. 28, 1988 describes an electrohydraulic system for leveling the dump box of a semi trailer dump vehicle. The system includes electric and hydraulic circuitry which releases all hydraulic pressure from the leveling struts when the dump box is in its lowered position. Thus, the trailer cannot be leveled before dumping operations begin. Leveling is entirely dependent upon the vehicle operator, who must position the trailer in an area having no more than a two degree lateral slope, according to the limits disclosed in the British patent publication. If two degrees or more of lateral slope is encountered, the operator must move the vehicle and reposition it for another attempt. The present invention allows the simultaneous operation of the leveling struts with the dump box lift strut, thereby saving time during the dumping operation for greater efficiency, unlike the system of the British publication. Also, the present system may provide for alarm and/or dump box lift cutout means if a predetermined maximum tilt angle is reached.
Finally, German Patent Publication No. 3,807,018 published on Sep. 14, 1989 illustrates a pneumatically operated leveling system. The English abstract states that the system may be trimmed automatically or manually during dumping operations, but no schematic or componentry is shown for such a system, and moreover, no warning or disabling means is apparent from the disclosure, which means may be included in the present system.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.